Objective-C的

- (void)viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator

迅速

func viewWillTransitionToSize(size: CGSize,withTransitionCoordinator coordinator: UIViewControllerTransitionCoordinator) {
    coordinator.animateAlongsideTransition(nil,completion: {
    if UIDevice.currentDevice().orientation.isLandscape.boolValue {
        print("landscape")
    } else {
        print("portrait")
    }
}